My opinion: DSi-XL will give you the best exprerience! I've got a couple of normal ones but I never touch them, only the XL gets used (for playing NDS/DSi games).
And in addition to the previous post:
File corruption usually occurs when writing to a disk is interrupted (or takes too long). this might be due to powerloss (or spike). Ejection whilst writing is the reason why you should always eject a removable drive in software before janking it out, you force it to finish it's read and writing...
@FAST6191 has made some nice comments with info and links on GBA cheats..
https://gbatemp.net/threads/how-do-i-get-started-with-cheat-code-making.566530/post-9078883
Normally you just put the save where the savegames are stored (same folder as the roms or a saves folder depending on your setup) having the same name as the rom, just another extension normally .sav .
Some wear old clothes and look old, others think wear vintage clothes and look cool. I think the GBA is in the cool corner and guess where the ds phat is...
A photo of the pcb would help, then you know might found out which card you've got and which flashcard files you need.
Downloading roms is a google problem.
I buy there regularly: compare, check, check the size, check the price and don't buy SD-cards.
I saw people ordering a gun getting the picture of the gun (exactly as in the description if you read all the way down). I bought rp2040's, leds electronics...